It has been conventionally known that an injection aperture located at a nozzle tip portion may corrode due to the adhesion of condensed water formed by dew condensation of water on the nozzle tip portion of an injector that injects fuel into a cylinder of an internal combustion engine. Whether dew condensation forms on the nozzle tip portion is affected by the relation between the temperature of the nozzle tip and a dew point of the atmosphere in the cylinder. From this perspective, Patent Document 1 suggests estimating the temperature of the nozzle tip and then adjusting an EGR quantity based on the estimated temperature of the nozzle tip to reduce the corrosion.